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Lubrication

SNL and SE plummer (pillow) block housings in the 2, 3, 5 and 6 series with standard seals are intended for grease lubrication. For oil lubrication, SNL housings with oil seals (Housings for oil lubrication) or

The lubricant should be selected based on the operating conditions of the bearing. For additional information, refer to Lubricant selection.

Initial grease fill

If no other requirements exist, the free space in the bearing should be completely filled with grease and the free space in the housing should be filled to 20 to 40% of its volume. To avoid over-filling, markings at each corner of SE housing base indicate the proper grease level for an initial 20 or 40% fill of the free space between housing and bearing (fig. 1). A 40% grease fill is required when bearings have to be relubricated from the side, while a 20% grease fill is used when bearings are relubricated via the outer ring.

For highly contaminated environments and slow speeds, fill the housing to 70–80%. For best protection against contaminants, use the SKF Three-Barrier Solution. For additional information, contact the SKF application engineering service.

Quantities for 20 and 40% grease fills are listed in table 1. The values are valid for a typical lithium grease (about 0,95 g/cm3). They include grease for the bearing and the four-lip seals or the sealing washers of V-ring seals. The grease to fill labyrinth seals or taconite heavy-duty seals is not included. For sealed bearings, the values have to be adjusted.

In most applications, the initial grease fill will adequately lubricate the bearing until the grease is exchanged during the next planned maintenance interval.

Relubrication

SNL and SE housings have two holes that have been drilled and tapped for an AH 1/8-27 PTF grease fitting. On a new housing, the holes are covered by plastic plugs. These plugs should be replaced with the grease fitting and threaded plug supplied with the housing.

If a larger grease fitting or other equipment has to be used, an adapter to change to a G 1/4 thread is available (Accessories).

Dimples cast into the top of the housing cap indicate alternative positions where holes can be drilled and tapped to accommodate a grease fitting for bearing or seal relubrication.

The hole in the centre of the cap should be used to relubricate spherical roller bearings with a relubrication feature (a lubrication groove and holes in the outer ring) (fig. 4). When applying grease via the relubrication feature, the shaft should be rotating. Narrow bearings (dimension series 13 and 22) in the locating position can be displaced axially, so that the relubrication groove in the bearing does not line up with the relubrication hole in the housing cap. Make sure the bearing is sufficiently centred when relubricating.
The hole in a SE housing cap for relubrication through the centre of the bearing is positioned off-centre relative to the shaft axis (fig. 5).

When relubricating from the side, which is typically necessary for self-aligning ball bearings and CARB toroidal roller bearings, the offset hole in the housing should be used. An integrated flange in the housing guides grease from the grease fitting directly to the rolling elements (fig. 6). This grease guiding system is available on housings from sizes 216 and 516-613 upwards.

When bearings mounted on an adapter sleeve have to be relubricated from the side, the grease should be introduced from the side opposite the lock nut.

When bearings mounted at the end of a shaft have to be relubricated from the side, the grease should be applied at the point closest to the end cover.

When relubricating bearings from the side in housings with V-ring seals, mount an additional V-ring inside the housing on the side where grease is applied (fig. 7). This forces the grease to travel through the bearing and exit the housing on the opposite side.

SKF can supply an appropriate V-ring together with a splash plate that fits in the seal groove to cover a bit more than the top half of the housing. These sets are identified by the series designation ASNA followed by the housing size identification and the suffix V, e.g. ASNA 516 V.

When four-lip seals (TSN .. L) or felt seals (TSN .. C or FS 170) are used, grease cannot escape via the seals. If relubrication is required, the housing should have a grease escape hole.

SNL and SE housings can be supplied with a grease escape hole (designation suffix V). A grease escape hole can be drilled into the SNL housing using the dimensions provided in table 2.
For SE housings the grease escape hole is parallel to the shaft (fig. 8) for easier access after the housing is mounted. The hole is threaded and plugged.